Torque transferring device

ABSTRACT

A device for transferring a torque may comprise an outer tubular component enclosing a shaft, the diameter of which is only slightly less than the cylindrical, internal surface of the outer component. These two components cooperate through the intermediation of balls operating in parallel, matching grooves in the two components. To ensure a recirculation of the balls in unloaded condition and to ensure a smooth running of the balls, the grooves are arranged in at least three pairs in which two grooves on opposite sides of a ridge in the inner component will cooperate with two grooves arranged at opposite sides of a groove in the outer member to form two runways, which are each connected to a return passage in the outer component.

C Umted States Patent [151 3,659,435 Nilsson [4 1 May 2, 1972 s41 TORQUETRANSFERRING DEVICE FoREIGN PATENTS OR APPLICATIONS [72] Inventor: venWalter N ss n. a dalen. Sweden 955,913 4/1964 Great Britain ..64/23 [73]Assignee: SKF Industrial Trading and Development Company N.V.,Amsterdam, Netherlands hammer-Edward Favors [22] F] d 7 1970Attorney-Howson and Howson l e ay [21] Appl. No.: 35,456 ABSTRACT Adevice for transferring a torque may comprise an outer tu- [301 ForeignApplication P i rit Dgla bular component enclosing a shaft, the diameterof which is only slightly less than the cylindrical, internal surface ofthe May 9, 1969 Sweden ..6573/69 outer component These two componentscooperate through the interrnediation of balls operatin in parallel,matchin s2 U.S. Cl. .64/23.7 g g [51] Int Cl M 3/06 groovesin the twocomponents. [58] Field 0! Search... ..64/23, 23.7 T ensure aregircularion of the balls in unloaded condition and to ensure a smoothrunning of the balls, the grooves are [56] References Cmd arranged in atleast three pairs in which two grooves on op- UNITED STATES PATENTSposite sides of a ridge in the inner component will cooperate r with twogrooves arranged at opposite sides of a groove in the et al outer memberto form two runways are each con. 3 gf y a nected to a return passage inthe outer component. ,0 anc ar et a 2,945,366 7/1960 Sears ..64/23.7 2Claims, 5 Drawing Figures PMENTEDMAY 2 I972 v mvzu'ronz SVEN WALTERNILSSON TTTT 5.

I TORQUE TRANSFERRING DEVICE BACKGROUND OF THE INVENTION The presentinvention refers to a device adapted to transfer a torque between twocomponents which are axially displaceable in relation to each otherthrough the intermediation of balls operating in axially extendinggrooves in the components. The aim of the invention is to provide adevice which makes possible a re-circulation of the balls without anyload being imposed thereon, and furthermore to arrange the runways forthe balls with bends having appropriate radii to ensure a smooth runningof the balls. By a slight increase of the ball diameter above thenominal value of the groove it will furthermore be possible to maintainthe desired clearance within the unit.

SUMMARY OF THE INVENTION According to the invention one of thecomponents, which is tubular and encloses the other component, isinwardly defined by a substantially cylindrical surface, which the othercomponent is defined by a substantially cylindrical external surfacehaving slightly smaller diameter than the intemal surface of the outercomponent. Each component is provided with at least three pairs ofgrooves running in parallel and having a cross section forming part of acircular arc. Each pair of grooves in the internal component is locatedto fit in between the grooves at a juxtaposed pair of grooves in theouter component, in such a manner that the lines defining the crosssections of one groove in the outer member and one groove in theinternal member will form part of a common circle, the outer memberbeing provided with bores and passages to bring about a continuousre-circulation of the balls.

One embodiment of the invention will below be described with referenceto the accompanying drawings as utilized in a device where a tubularbody is mounted on a shaft, and is designed to transfer a torque to thelatter, or where reversely, the shaft may transfer a torque to thetubular member, while simultaneously an axial displacement of thetubular member in relation to the shaft may take place.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a longitudinal sectionthrough the outer component taken along line 1-] in FIG. 2;

FIG. 2 is a cross section through the device taken along line II-II inFIG. 1;

FIG. 3 shows a cross section taken along line III-III in FIG.

FIG. 4 is a cross section taken along line IV-IV in FIG. 1; and

FIG. 5 shows a perspective view of a guiding member.

DESCRIPTION OF THE PREFERRED EMBODIMENT The shaft is tubular and isgenerally denoted by 10. It has a general circular cross section, but inthe body thereof four axially extending grooves 11 are formed spacedapart 90 by axially extending recesses 12 being milled from the body ofthe shaft. The outer tubular component is denoted by 13 and has aconsiderably shorter length than the shaft. The external surface of theouter component may have arbitrary shape, to make it suitable forfitting into a machine element. It is here shown cylindrical with twoexternal recesses 14, which facilitate the desired connection to acertain type of machine elements. The internal surface of the componentis also cylindrical, and in the same four axially extending grooves 15are formed, space apart by 90. These recesses are somewhat broader thanthe ridges 11 at the inner component, and it should be noted that theinner component is completely circumscribed by the outer component, insuch a manner that a mechanical contact between the parts may beavoided.

The transfer of the torque is brought about by means of a number ofballs 16 only, which are fitted into runways formed between the groovesin the components. Said runways comprising parts at the ridges l1 and inthe recesses 15. To each side of a ridge there is thus an axiallyextending groove 17, having a cross section defined by a line formingabout one quarter of a circle. In the corresponding manner there is ateach side of the recess 15 a similar groove 18, which likewise isdefined by a line forming about one quarter of a circle. These twoquarter circles form parts of a common circle, which defines the runwayinto the balls are fitted.

By making the balls 16 slightly larger than this circle the desiredclearance between the components of the device may be maintained. Thisadjustment of the clearance may also be brought about by dividing theouter component 13 into two or more parts, which may be adjusted inrelation to each other. It is also possible to make axially extendingslots in the component I3, and to force the parts separated by the slotstowards each other by means of screws or the like in order to reduce theclearance.

A torque may thus be transferred between the two components by means ofeight rows of balls, and during a relative axial displacement betweenthe components it is necessary to provide a re-circulation of the ballsfrom the rearmost end of the grooves to the forward ends, as counted, inthe direction of movement. This re-circulation shall take place withoutthe balls being subjected to any load during this part of the movement.The balls must in other words have a possibility freely to pass throughthe body of one of the components. FIG. 1 shows that the outer component13, at each end is provided with a lid, 19 and 20, respectively. Inthese lids passages 22 are formed by means of guide members 21 beingfitted into recesses. Each passage in the lids is connected to a runwaycomposed of two grooves 17 and 18 and this passage is continued by anaxially extending return bore 23 in the outer component. For each pairof runways l7, 18 there is such thus one return bore 23, and for the tworunways, which are located to each side of a ridge 1], there will thusbe two return bores 23. These are in the manner best shown in FIG. 3arranged in a plane 24, which forms a tangent to the circle defining theplane of division between the two components 10 and 13. By thisarrangement, the cross sectional thickness of the outer member 13 may bemaintained at a minimum and still provide a desired radius of thetransfer passage 22 to permit smooth circulation of the balls. Thus, thedevice of the present invention may be made more compactly as compared,for example, to devices wherein the ball return passage is locatedradially outwardly of the ball path between the members.

FIG. 5 shows a perspective view of a guiding member 21. This consists ofa head 25, which is formed as a half cylinder provided with an externalgroove 26 corresponding to the shape of the ball. The member is providedwith a shaft 27, which facilitates the mounting and locking thereof inthe lid.

The drawings shows a device having four ridges. In order to obtain asatisfactory function three ridges must at least be provided, butdepending upon the size of the device and the torque to be transferred,the number of ridges and runways may of course be increased above four.

What I claim is:

1. In a device for transferring a torque between inner and outer memberswhich are axially displaceable in relation to each other through theintermediation of balls operating in juxtaposed, axially extendinggrooves in the members, the outer member being tubular and enclosing theinner member and having an inner substantially cylindrical surface, theinner member having a substantially cylindrical external surface of aslightly smaller diameter than the internal surface of the outer memberto define an annular space therebetween, the improvement that eachmember is provided with at least three pairs of grooves running inparallel and having a cross section forming part of a circular arc, andwhere each pair of grooves in the inner member is located to fit inbetween the grooves at a juxtaposed pair in the outer member in such amanner that the lines defining the cross sections of one groove in theouter member and of one groove in the inner member will form part of acommon circle defining a ball runway, said grooves of recirculationbores associated with the runways of each pair being disposed in a planetangent to the annular space between the members.

2. A device as claimed in claim 1 including guide members forming theend passages of the recirculation bores, said guide members being fittedinto recesses in lid parts at the outer axial ends of the outer member.

1. In a device for transferring a torque between inner and outer memberswhich are axially displaceable in relation to each other through theintermediation of balls operating in juxtaposed, axially extendinggrooves in the members, the outer member being tubular and enclosing theinner member and having an inner substantially cylindrical surface, theinner member having a substantially cylindrical external surface of aslightly smaller diameter than the internal surface of the outer memberto define an annular space therebetween, the improvement that eachmember is provided with at least three pairs of grooves running inparallel and having a cross section forming part of a circular arc, andwhere each pair of grooves in the inner member is located to fit inbetween the grooves at a juxtaposed pair in the outer member in such amanner that the lines defining the cross sections of one groove in theouter member and of one groove in the inner member will form part of acommon circle defining a ball runway, said grooves of each pair in theouter member being located at opposite sides of a recess in said outermember and said grooves in the inner member being located at oppositesides of an axial ridge formed within the circular contour of the innermember by means of two axially extending recesses therein, the outermember being provided with axially extending recirculation bores and endpassages interconnecting the ends of each recirculation bore with theends of a corresponding ball runway to permit a continuous recirculationof the balls, the axes of the recirculation bores associated with therunways of each pair being disposed in a plane tangent to the annularspace between the members.
 2. A device as claimed in claim 1 includingguide members forming the end passages of the recirculation bores, saidguide members being fitted into recesses in lid parts at the outer axialends of the outer member.